1. Field of the Invention
The present invention relates to a doping apparatus and a doping method, more specifically to doping technology used for forming a dopant region such as source and drain regions in a field-effect transistor (FET).
2. Description of the Related Art
In semiconductor elements (devices) such as a field-effect transistor and a thin-film transistor, doping is carried out to control their electric characteristics. The doping is a method for introducing a dopant such as arsenic (As), boron (B), and phosphorus (P) into a semiconductor film. Depending on the type of the dopant introduced into the semiconductor element, the semiconductor elements can be obtained p type in which holes are the majority carrier and n type in which electrons are the majority carrier. Therefore, electric characteristics of semiconductor elements (for example, a threshold voltage in thin-film transistors) have been controlled by the amount of dopant (dosage) which is doped, activation ratio of the dopant, and carrier concentration.
The activation ratio of a dopant is represented by the ratio of the amount of a dopant introduced in a semiconductor film and the amount of actually activated dopant. The activated dopant generates carriers. When the activation ratio of a dopant is 100%, the concentration of a dopant becomes equal to the concentration of carriers.
Characteristics of the elements have been conventionally inspected upon completion of semiconductor element fabrication. This information is fed back to a fabrication process and the doping method such as the amount of a dopant and doping rate is adjusted.
On the other hand, secondary ion mass spectroscopy (SIMS), spread resistance method (SR), and the like are used as methods for measuring the aforementioned dopant concentration (for example, see Patent Document 1).
[Patent Document 1]
Japanese Patent Laid-Open No. H11-23498